A bellows pump is configured by: a pump body which comprises a suction path and discharge path for a to-be-transported fluid; a bellows which is placed in a state where one end is airtightly fixed to the pump body to form a closed space with respect to the pump body; and an actuation plate which is attached to the other end of the bellows so as to cause the bellows to expand and contract with respect to the pump body. As examples of such a bellows pump, a single-bellows type disclosed in Patent Literature 1, and a double-bellows type (reciprocating pump) disclosed in Patent Literature 2 are known.
In a bellows pump which is a displacement pump, it is known that, in the timing of switching between suction due to the expansion of a bellows and discharge due to contraction of the bellows, a large pressure change (pressure rise) is momentarily produced. In the case where the fluid is liquid such as water, the change is shock vibration which is also called “water hammer”. Vibration caused by the large pressure change is transmitted to an apparatus or a pipe, thereby producing a possibility that inconveniences such as that particles are generated, and that various portions are broken (for example: a quartz-made tank which is connected to the pump through a pipe cracks or breaks) may occur.
Conventionally, therefore, countermeasures that the flow rate in the pipe is reduced to suppress vibration, and that an accumulator or the like is added to absorb generated vibration, thereby relaxing vibration are taken. However, the former vibration suppressing means is in summary to reduce the discharge amount of the pump, and hence there is a disadvantage that the performance is lowered, and, in the case of the latter vibration relaxing means, problems such as that the installation place is made large, and that the cost is increased occur.
As described above, in the proposed countermeasures for suppressing or eliminating shock vibration which is generated because of the structure of a bellows pump in the timing of switching between suction and discharge, without causing performance reduction and increases of the installation place and the cost, there remains room for further improvement.